[llvm] [AMDGPU] Use a consistent DwarfEH register flavour (PR #84513)

[Scott Linder via llvm-commits]

https://github.com/slinder1 approved this pull request.

Thank you for tracking this down! I'm still not sure I understand how the `IsEH` distinction functions generally; did you happen to get an understanding of why the call-site you reference knows it can request with `IsEH == true`? If not, I still don't think we have to deeply understand this as I don't suspect we will ever want to have a split encoding for `IsEH` vs `other`.

https://github.com/llvm/llvm-project/pull/84513